Don't miss it if on your way: Xiakou fort, ancient village and great wall
Entrance is free
Plenty of good spots to camp between the highway and the entrance.
I'm sure you can pitch your tent in the parking or inside.
Many toilets available everywhere.
You can charge your devices at the touristic centre at the entrance
You should be able to access from Xinhe Post Station 23km further north and ride/drive along the wall all the way in a much quieter road (the road is terrible and with a lot of lorries even if there is a parallel highway)
more or less here:
38.653931, 101.275185